Macros, like Trac itself, are written in the [http://www.python.org/ Python programming language]. They are very simple modules, identified by the filename and should contain a single `execute()` function. Trac will display the returned data inserted into the HTML representation of the Wiki page where the macro is called.

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Macros, like Trac itself, are written in the [http://python.org/ Python programming language].

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It's easiest to learn from an example:

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For more information about developing macros, see the [trac:TracDev development resources] on the main project site.

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== Implementation ==

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Here are 2 simple examples showing how to create a Macro with Trac 0.11.

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Also, have a look at [trac:source:tags/trac-0.11/sample-plugins/Timestamp.py Timestamp.py] for an example that shows the difference between old style and new style macros and at the [trac:source:tags/trac-0.11/wiki-macros/README macros/README] which provides a little more insight about the transition.

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=== Macro without arguments ===

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It should be saved as `TimeStamp.py` as Trac will use the module name as the Macro name

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{{{

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#!python

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# MyMacro.py -- The world's simplest macro

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from datetime import datetime

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# Note: since Trac 0.11, datetime objects are used internally

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def execute(hdf, args, env):

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return "Hello World called with args: %s" % args

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from genshi.builder import tag

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from trac.util.datefmt import format_datetime, utc

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from trac.wiki.macros import WikiMacroBase

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class TimeStampMacro(WikiMacroBase):

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"""Inserts the current time (in seconds) into the wiki page."""

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revision = "$Rev$"

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url = "$URL$"

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def expand_macro(self, formatter, name, args):

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t = datetime.now(utc)

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return tag.b(format_datetime(t, '%c'))

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}}}

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You can also use the environment (`env`) object, for example to access configuration data and the database, for example:

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=== Macro with arguments ===

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It should be saved as `HelloWorld.py` (in the plugins/ directory) as Trac will use the module name as the Macro name

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{{{

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#!python

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def execute(hdf, txt, env):

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return env.config.get('trac', 'repository_dir')

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from trac.wiki.macros import WikiMacroBase

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class HelloWorldMacro(WikiMacroBase):

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"""Simple HelloWorld macro.

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Note that the name of the class is meaningful:

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- it must end with "Macro"

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- what comes before "Macro" ends up being the macro name

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The documentation of the class (i.e. what you're reading)

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will become the documentation of the macro, as shown by

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the !MacroList macro (usually used in the WikiMacros page).

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"""

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revision = "$Rev$"

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url = "$URL$"

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def expand_macro(self, formatter, name, args):

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"""Return some output that will be displayed in the Wiki content.

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`name` is the actual name of the macro (no surprise, here it'll be

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`'HelloWorld'`),

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`args` is the text enclosed in parenthesis at the call of the macro.

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Note that if there are ''no'' parenthesis (like in, e.g.

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[[HelloWorld]]), then `args` is `None`.

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"""

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return 'Hello World, args = ' + unicode(args)

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# Note that there's no need to HTML escape the returned data,

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# as the template engine (Genshi) will do it for us.

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}}}

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Note that since version 0.9, wiki macros can also be written as TracPlugins. This gives them some capabilities that “classic” macros do not have, such as being able to directly access the HTTP request.

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For more information about developing macros, see the [http://projects.edgewall.com/trac/wiki/TracDev development resources] on the main project site.

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=== {{{expand_macro}}} details ===

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{{{expand_macro}}} should return either a simple Python string which will be interpreted as HTML, or preferably a Markup object (use {{{from trac.util.html import Markup}}}). {{{Markup(string)}}} just annotates the string so the renderer will render the HTML string as-is with no escaping. You will also need to import Formatter using {{{from trac.wiki import Formatter}}}.

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----

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See also: WikiProcessors, WikiFormatting, TracGuide

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If your macro creates wiki markup instead of HTML, you can convert it to HTML like this: